That doesn't change the fact, as clearly demonstrated, that the area was a swamp. That was the purpose of the causeway as well as the French not building any more bridges. It would not have been practical and the building of small one-man-at-a-time bridges would have been a waste of resources and time.
The bottom line is that the bridge over the Elster was not supposed to be blown until the rear guards had crossed. Dulauloy and Montfort were responsible for the incompetence of blowing it prematurely.
You're missing the point entirely and that is merely incredible.
By the way, the causeway and bridges over the Elster ran east-west, not north south. The Elster and Pleisse ran north-south.